Advertisement

Influence of neck shaft angle of humerus in prosthesis design

  • Sajan Skaria
    Correspondence
    Corresponding author. Department of Anatomy, American International Institute Of Medical Sciences, Near Transport Nagar Bedwas, Airport Road, Udaipur, 313001, Rajasthan, India.
    Affiliations
    Department of Anatomy, SBKSMI&RC Sumandeep Vidyapeeth Deemed to be University, Piparia, Vadodara, 391760, Gujarat state, India
    Search for articles by this author
  • Manoj Kulkarni
    Affiliations
    Department of Anatomy, SBKSMI&RC Sumandeep Vidyapeeth Deemed to be University, Piparia, Vadodara, 391760, Gujarat state, India
    Search for articles by this author
  • Achleshwar Gandotra
    Affiliations
    Department of Anatomy, SBKSMI&RC Sumandeep Vidyapeeth Deemed to be University, Piparia, Vadodara, 391760, Gujarat state, India
    Search for articles by this author
Published:October 20, 2022DOI:https://doi.org/10.1016/j.jcot.2022.102045

      Abstract

      Background

      A better understanding of the proximal humerus is essential for anatomical reconstruction of the glenohumeral joint during prosthetic replacement. The neck-shaft angle is critical for correct calcar screw positioning when fixing a proximal humeral fracture with a locking plate. It's essential for exact implant placement and treatment of any soft-tissue or bone pathology. Improper implants cause discomfort and post-operative complications, therefore understanding the humeral neck shaft angle is fundamental in the design and manufacturing of prostheses. This study looked into the necessity regional data of the humeral neck shaft angle (NSA) and its importance in shoulder prosthesis manufacturing.

      Method

      This cross-sectional investigation was conducted on 300 dry cadaveric humeri of unknown gender and age that were free of damage or deformity. The Goniometer was used to measure the neck shaft angle. The data was analysed using SPSS software. The standard deviation and mean were calculated. The statistical difference between the right and left humeri was assessed using the students' t' test.

      Observations

      The NSA of the humerus was 131.265.82° on average. The NSA mean values were substantially higher on the right side. A statistically significant difference between the right and left humeri was revealed by a P value of 0.001.

      Conclusion

      Success of the shoulder arthroplasty demands anatomical reconstruction of the normal neck-shaft angle of the humerus. Racial variations in the morphometry of the neck-shaft angle needs to be considered in prosthesis design.

      Keywords

      1. Introduction

      In the late 1990s, a thorough investigation of shoulder anatomy as it relates to prosthetic geometry commenced. It has become evident that normal anatomy demonstrates a considerable measure of individual variation. Humeral implants have been widely popular in recent times, owing to a broader understanding of shoulder anatomy and function. Surgeons executing shoulder arthroplasty should have a comprehensive understanding of glenohumeral anatomy and modern design components. Fracture of Proximal humerus are more frequent among older people with osteoporosis and it constitutes about 4–5% of all fractures.
      • Palvanen M.
      • Kannus P.
      • Niemi S.
      • Parkkari J.
      Update in the epidemiology of proximal humeral fractures.
      These minimally displaced fractures can, in most situations, be treated conservatively.
      • Gaebler C.
      • McQueen M.M.
      • Court-Brown C.M.
      Minimally displaced proximal humeral fractures: epidemiology and outcome in 507 cases.
      Surgical intervention is essential in 15–20% of displaced cases.
      • Palvanen M.
      • Kannus P.
      • Niemi S.
      • Parkkari J.
      Update in the epidemiology of proximal humeral fractures.
      In shoulder arthroplasty, the neck-shaft angle is a critical factor in defining the varus and valgus angles of the prosthesis.
      • Iyem C.
      • Serbest S.
      • Inal M.
      • et al.
      A morphometric evaluation of the humeral component in shoulder arthroplasty.
      The neck-shaft angle, also known as inclination angle is produced by a line passing between the shaft's central intramedullary axis and a line perpendicular to the articular segment's base. It is a method of determining the coronal displacement of the proximal humerus.
      • Paavolainen P.
      • Björkenheim J.M.
      • Slätis P.
      • Paukku P.
      Operative treatment of severe proximal humeral fractures.
      ,
      • Agel J.
      • Jones C.B.
      • Sanzone A.G.
      • Camuso M.
      • Henley M.B.
      Treatment of proximal humeral fractures with Polarus nail fixation.
      It may be used to plan arthroplasty and osteotomy, as well as to assess the effects of osteosynthesis. Neck-shaft angle is approximately 135° in most of the cases.
      • Assunçao J.
      • Malavolta E.
      • Beraldo R.
      • Gracitelli M.
      • Bordalo-Rodrigues M.
      • Ferreira Neto A.
      Impact of shoulder rotation on neck-shaft angle: a clinical study.
      A prosthetic design with a fixed NSA allows for the reproduction of the humeral center of rotation with a simple and more cost-effective prosthetic solution.
      Surgeons executing shoulder arthroplasty should have a comprehensive understanding of glenohumeral anatomy and modern design components. It has become evident that normal anatomy demonstrates a considerable measure of individual variation. Same kind of implants are not suitable for different populations as the angulations varies with populations. The current study aimed to make a baseline data on the neck-shaft angle of humerus in Western Indian population.

      2. Materials and methods

      The cross sectional analytical study was approved by the Institutional Ethics Committee. The dried and preserved humeri (300, 150 Right & 150 Left) for the study were obtained from the Anatomy department of Medical Institutes of Western India during the period 2019 June −2021 December. The permission for the study was obtained from the head of the institute prior to the study. The specimen were placed on a flat surface. Lower end of the humerus was slightly rotated laterally to negate the torsion of upper epiphysis so that the neck shaft angle is clearly seen. A midpoint of the anatomical neck was marked on the anterior aspect using Vernier Calliper. A line intersecting this point was marked as the head - neck axis. Axis of the shaft was recognized by finding midpoints of the shaft using Vernier Calliper. The angle formed between these two axes was measured using Goniometer
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      (Fig. 1). The measurements were recorded by single observer and repeated thrice to remove intra-observer variation (see Fig. 3) (see Fig. 4) (see Fig. 5) (see Fig. 2).
      Fig. 1
      Fig. 1Measurement of neck shaft angle using goniometer.
      Fig. 2
      Fig. 2Neck shaft angle of Right humerus 144°
      Fig. 3
      Fig. 3Neck shaft angle of Right humerus 120°
      Fig. 4
      Fig. 4Neck shaft angle of Left humerus 135°
      Fig. 5
      Fig. 5Neck shaft angle of Left humerus 125°

      2.1 Inclusion criteria

      Non pathological intact dry humeri of unknown age and gender were used for the analysis.

      2.2 Exclusion criteria

      Bones with defects, arthritic deformity or damage were excluded.

      3. Statistical analysis

      The statistical analysis of the study was performed by SPSS (Statistical Package for the Social Sciences) for windows version 18.0 (SPSS Inc., Chicago, IL,USA). Mean and standard deviation were calculated. Unpaired student's ‘t’ test was used to compare the means. A value of p < 0.05 value was accepted as statistically significant.

      4. Results

      The data related to the findings of the study is tabulated in Table 1. The mean NSA of the humerus (300) was 131.26 ± 5.82°. The findings of the study were similar to those of reported by various authors.
      • Assunçao J.
      • Malavolta E.
      • Beraldo R.
      • Gracitelli M.
      • Bordalo-Rodrigues M.
      • Ferreira Neto A.
      Impact of shoulder rotation on neck-shaft angle: a clinical study.
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      • Zhang L.
      • Yuan B.
      • Wang C.
      • Liu Z.
      Comparison of anatomical shoulder prostheses and the proximal humeri of Chinese people.
      Statistically significant difference were discovered between right and left bones (P-value = 0.001). The left humeri showed the average NSA of 130.15 ± 3.06° and the right bones it was 132.37 ± 7.48°.
      Table 1Neck shaft angle of humerus.
      NMean (±S.D.)Std. Error of Meant-valuep-value
      Students' ‘t’ test for the difference of means; p-value <0.0001 was considered as statistically significant.
      Left Humerus150130.15 ± 3.06°0.253.350.001
      Right Humerus150132.37 ± 7.48°0.61
      Total300131.26 ± 5.82°0.34
      a Students' ‘t’ test for the difference of means; p-value <0.0001 was considered as statistically significant.

      5. Discussion

      The use of shoulder prostheses started in 1973.
      • De Lude J.A.
      • Bicknell R.T.
      • Mac Kenzie G.A.
      • Ferreira L.M.
      • Dunning C.E.
      An anthropometric study of the bilateral anatomy of the humerus.
      Many investigations have been done since then to characterize the pathological variations in the proximal humerus and the importance of restoration of normal anatomy.
      • De Lude J.A.
      • Bicknell R.T.
      • Mac Kenzie G.A.
      • Ferreira L.M.
      • Dunning C.E.
      An anthropometric study of the bilateral anatomy of the humerus.
      • Hertel R.
      • Knothe U.
      • Ballmer F.T.
      The geometry of the proximal humerus and implications for prosthetic design.
      • Iannotti J.P.
      • Gabriel J.P.
      • Schneck S.L.
      • Evans B.G.
      • Misra S.
      The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders.
      • Roche C.
      • Angibaud L.
      • Flurin P.H.
      • Wright T.
      • Fulkerson E.
      Anatomic validation of an anatomic shoulder system.
      Several biomechanical studies showed that a modular prosthetic design brings better clinical results.
      • Roche C.
      • Angibaud L.
      • Flurin P.H.
      • Wright T.
      • Fulkerson E.
      Anatomic validation of an anatomic shoulder system.
      • Harryman D.T.
      • Sidles J.A.
      • Harris S.L.
      • Lippitt S.B.
      • Matsen F.
      The effect of articular conformity and the size of the humeral head component on laxity and motion after glenohumeral arthroplasty. A study in cadavera.
      • Nyffeler R.W.
      • Sheikh R.
      • Jacob H.A.
      • Gerber C.
      Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study.
      Variable inclination angle implants require the surgeon to respect the humeral head as much as possible along the anatomic neck, and later offer either variable or adjustable geometries to fit the resulting inclination angle. Implants with a set inclination angle (anywhere within the usual region), on the other hand, direct the surgeon to perform an osteotomy at this inclination, then modify the fit with further canal preparation and amendments as needed.
      The mean NSA of the humerus falls in the range of 135°–140°, but the literature demonstrates significant individual variation (range, 125°–150°).
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      The mean NSA of the humerus in the present work was 131.26° ± 5.82°. Malavolta et al. evaluated the neck-shaft angle of 18 cadaveric humeri in different positions and reported an NSA of 137° ± 4° in the neutral position.
      • Malavolta E.A.
      • Assunçao J.H.
      • Pagotto R.A.
      • et al.
      The rotation of the humeral head does not alter the radiographic evaluation of the head-shaft angle.
      Assunçao JH et al. documented a mean NSA of 132 ± 6° in Brazilian population.
      • Assunçao J.
      • Malavolta E.
      • Beraldo R.
      • Gracitelli M.
      • Bordalo-Rodrigues M.
      • Ferreira Neto A.
      Impact of shoulder rotation on neck-shaft angle: a clinical study.
      Iyem C et al. reported 136.4° ± 3.5° NSA in the Turkish population.
      • Iyem C.
      • Serbest S.
      • Inal M.
      • et al.
      A morphometric evaluation of the humeral component in shoulder arthroplasty.
      These authors measured anteroposterior radiographs of the shoulder joint. Jeong et al. studied 2058 humeri and noted an average neck-shaft angle of 134.7°.
      • Jeong J.
      • Bryan J.
      • Iannotti J.P.
      Effect of a variable prosthetic neck-shaft angle and the surgical technique on replication of normal humeral anatomy.
      Goldberg RW et al. studied the NSA and version of 1104 cadaveric humeri and reported that the variables are independent of sex and age. They found substantial disparities between NSA and race.
      • Goldberg R.W.
      • Williamson D.F.
      • Hoven H.A.
      • Liu R.W.
      Humeral version and neck-shaft angle correlated with demographic parameters in a study of 1104 cadaveric humeri.
      Hertel R et al. measured the NSA directly on 200 dry humeri and reported that the NSA ranged between 132° and 142°.
      • De Lude J.A.
      • Bicknell R.T.
      • Mac Kenzie G.A.
      • Ferreira L.M.
      • Dunning C.E.
      An anthropometric study of the bilateral anatomy of the humerus.
      NSA is an important parameter in shoulder arthroplasty as the angular movement of the post operative shoulder joint is greatly related to the varus and vulgus angle of the prosthesis. Iannotti discovered a link between NSA and the humeral head size.
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      He also stated that any NSA variation in the humeral component other than the anatomical NSA results in a lower displacement of the humeral head's rotational center; hence, results in the prominent greater tubercle.
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      Extreme varus and valgus are found to affect the postoperative results of humeral fracture and prosthetic restoration.
      • Solonen K.A.
      • Vastamaki M.
      Osteotomy of the neck of the humerus for traumatic varus deformity.
      Takase K et al. analysed the impact of NSA on the geometry of the glenohumeral joint, especially with lateral humeral offset. They did not find any correlation between the both.
      • Takase K.
      • Yamamoto K.
      • Imakiire A.
      • Burkhead Jr., W.Z.
      The radiographic study in the relationship of the glenohumeral joint.
      Longo U G et al. observed a positive outcome in terms of the range of motion like abduction, external rotation, and forward bending in the groups with an NSA of 155°, 145°, and 135°. They observed that an implant with NSA of 145° is good in terms of postoperative forward flexion and of with 135° is good in external rotation.
      • Longo U.G.
      • Gulotta L.V.
      • De Salvatore S.
      • et al.
      The role of humeral neck-shaft angle in reverse total shoulder arthroplasty: 155° versus <155°-A systematic review.
      Gobezie et al.
      • Gobezie R.
      • Shishani Y.
      • Lederman E.
      • Denard P.J.
      Can a functional difference be detected in reverse arthroplasty with 135° versus 155° prosthesis for the treatment of rotator cuff arthropathy: a prospective randomized study.
      were unable to detect any differences between humeral inclinations of 135° and 155° in postoperative forward flexion and external rotation values. Werner B et al. in their study found implant with lesser NSA enjoys impingement-free motion range and suggested the use of a 135° NSA model implant for smooth functioning of the post-operative shoulder.
      • Werner B.
      • Chaoui J.
      • Walch G.
      The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty.
      The impact of NSA of reverse humeral on anterior dislocation force, abduction moment, as well as impingement-free motion range were examined by Oh JH et al. They tested six cadaveric shoulders with 155°, 145°, and 135°. The 135° neck-shaft angle at 30° of external rotation and the 155° of internal rotation both greatly increased the anterior dislocation force. Although it was more stable when internally rotated, the 155° NSA was more susceptible to scapular impingement during adduction.
      • Oh J.H.
      • Shin S.J.
      • McGarry M.H.
      • Scott J.H.
      • Heckmann N.
      • Lee T.Q.
      Biomechanical effects of humeral neck-shaft angle and subscapularis integrity in reverse total shoulder arthroplasty.
      Bart Middernacht et al. in a critical review suggested the use of a prosthesis with 135° for gain in adduction motion and reduced notching. They pointed out that designs with an inclination of 155° increase the incidence of scapulohumeral conflict.
      • Middernacht B.
      • Tongel A.V.
      • De Wilde L.
      A critical review on prosthetic features available for reversed total shoulder arthroplasty.
      The normal variability of the humeral neck-shaft angle creates some difficult choices for prosthetic design. Anatomical restoration is successful only if the NSA of an implant system matches the NSA of the native humerus into which it is being implanted.
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      An anatomical head varus osteotomy results when the neck-shaft angle of a fixed-angle implant is smaller than that of the natural humerus. A valgus osteotomy is made for the anatomical NSA if the prosthesis' angle exceeds that of the natural humerus.
      • Iannotti J.P.
      • Lippitt S.B.
      • Williams Jr., G.R.
      Variation in neck-shaft angle: influence in prosthetic design.
      Changes in prosthesis design are necessary because of demographic or racial differences. Thus, the use of population-specific implants increases the functionality of the prosthesis. For prosthesis design, certain knowledge about the normal morphometry of proximal epiphysis of the humerus and glenoid part is critical.
      • Goldberg R.W.
      • Williamson D.F.
      • Hoven H.A.
      • Liu R.W.
      Humeral version and neck-shaft angle correlated with demographic parameters in a study of 1104 cadaveric humeri.
      Morphometric data of the proximal humerus thus play a vital role in the appropriate design of the humeral component.
      • Hertel R.
      • Knothe U.
      • Ballmer F.T.
      The geometry of the proximal humerus and implications for prosthetic design.
      This study is important because compatibility with normal anatomic structure must be taken into consideration in the design of the humeral component. The restricted shoulder motion and subluxation might result from an improper prosthesis.
      • Iyem C.
      • Serbest S.
      • Inal M.
      • et al.
      A morphometric evaluation of the humeral component in shoulder arthroplasty.
      The main reason for most shoulder arthroplasty post-operative problems is the inability of several current shoulder replacement methods to restore normal morphometry.
      • Wirth M.A.
      • Ondrla J.
      • Southworth C.
      • Kaar K.
      • Anderson B.C.
      • Rockwood C.A.
      Replicating proximal humeral articular geometry with a third-generation implant: a radiographic study in cadaveric shoulders.
      This study aims to demonstrate that each population's morphometric data differs from one another, and that prosthesis applications will be more successful if these variations are taken into account. In Table 2, the results of the present research are contrasted with those of investigations that were done on other ethnic communities. These findings demonstrated that there are variations in morphometric data of proximal humerus in different populations. Prosthesis manufacturers should consider these differences for postoperative success.
      Table 2Neck shaft angle of humerus reported in different population.
      Author And Year Of StudyPopulationNSA±SD
      Present study (2022)India131.26° ± 5.82°
      Goldberg RW et al. (2020)
      • Goldberg R.W.
      • Williamson D.F.
      • Hoven H.A.
      • Liu R.W.
      Humeral version and neck-shaft angle correlated with demographic parameters in a study of 1104 cadaveric humeri.
      America137° ± 6°
      Iyem C et al. (2017)
      • Iyem C.
      • Serbest S.
      • Inal M.
      • et al.
      A morphometric evaluation of the humeral component in shoulder arthroplasty.
      Turkey136.4° ± 3.5°
      Assunçao J H (2017)
      • Assunçao J.
      • Malavolta E.
      • Beraldo R.
      • Gracitelli M.
      • Bordalo-Rodrigues M.
      • Ferreira Neto A.
      Impact of shoulder rotation on neck-shaft angle: a clinical study.
      Brazil132° ± 6°
      Zhang et al. (2007)
      • Zhang L.
      • Yuan B.
      • Wang C.
      • Liu Z.
      Comparison of anatomical shoulder prostheses and the proximal humeri of Chinese people.
      China132.4° ± 4.7°
      Takase K et al. (2004)
      • Takase K.
      • Yamamoto K.
      • Imakiire A.
      • Burkhead Jr., W.Z.
      The radiographic study in the relationship of the glenohumeral joint.
      Japan140.4° ± 4.1°
      Hertel R et al. (2002)
      • Hertel R.
      • Knothe U.
      • Ballmer F.T.
      The geometry of the proximal humerus and implications for prosthetic design.
      Switzerland137° ± 3.62°
      McPherson et al. (1997)
      • McPherson E.J.
      • Friedman R.J.
      • An Y.H.
      • Chokesi R.
      • Dooley R.L.
      Anthropometric study of normal glenohumeral relationships.
      USA141° ± 8.6°

      6. Limitations

      Prosthesis manufacturers should consider these differences for postoperative success.
      The significant drawback of the study was that the humeri investigated were of unknown origin, age, and gender. The previous clinical conditions of the donors were unknown. It would have been better if these data were available.

      7. Conclusion

      The present study tried to make baseline data on the NSA of the humerus in the Western Indian people. The NSA values of this study were lesser than the data of western countries. These results show each population has variations in the NSA of the humerus. These differences between populations described could form a database for prosthesis manufacturers designing the humeral component. It is important to take care while calculating the NSA values since an excessive varus angle may result in subluxation and an excessive valgus angle can cause impingement in adduction.

      Declaration of competing interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      References

        • Palvanen M.
        • Kannus P.
        • Niemi S.
        • Parkkari J.
        Update in the epidemiology of proximal humeral fractures.
        Clin Orthop Relat Res. 2006; 442: 87-92
        • Gaebler C.
        • McQueen M.M.
        • Court-Brown C.M.
        Minimally displaced proximal humeral fractures: epidemiology and outcome in 507 cases.
        Acta Orthop Scand. 2003; 74: 580-585
        • Iyem C.
        • Serbest S.
        • Inal M.
        • et al.
        A morphometric evaluation of the humeral component in shoulder arthroplasty.
        Biomed Res. 2017; 28: 2666-2672
        • Paavolainen P.
        • Björkenheim J.M.
        • Slätis P.
        • Paukku P.
        Operative treatment of severe proximal humeral fractures.
        Acta Orthop Scand. 1983; 54: 374-379
        • Agel J.
        • Jones C.B.
        • Sanzone A.G.
        • Camuso M.
        • Henley M.B.
        Treatment of proximal humeral fractures with Polarus nail fixation.
        J Shoulder Elbow Surg. 2004; 13: 191-195
        • Assunçao J.
        • Malavolta E.
        • Beraldo R.
        • Gracitelli M.
        • Bordalo-Rodrigues M.
        • Ferreira Neto A.
        Impact of shoulder rotation on neck-shaft angle: a clinical study.
        Orthop Traumatol Surg Res. 2017; 103: 865-868
        • Iannotti J.P.
        • Lippitt S.B.
        • Williams Jr., G.R.
        Variation in neck-shaft angle: influence in prosthetic design.
        Am J Orthoped. 2007; 36: 9-14
        • Zhang L.
        • Yuan B.
        • Wang C.
        • Liu Z.
        Comparison of anatomical shoulder prostheses and the proximal humeri of Chinese people.
        J Eng Med. 2007; 221: 921-927
        • De Lude J.A.
        • Bicknell R.T.
        • Mac Kenzie G.A.
        • Ferreira L.M.
        • Dunning C.E.
        An anthropometric study of the bilateral anatomy of the humerus.
        J Shoulder Elbow Surg. 2007; 16: 477-483
        • Hertel R.
        • Knothe U.
        • Ballmer F.T.
        The geometry of the proximal humerus and implications for prosthetic design.
        J Shoulder Elbow Surg. 2002; 11: 331-338
        • Iannotti J.P.
        • Gabriel J.P.
        • Schneck S.L.
        • Evans B.G.
        • Misra S.
        The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders.
        J Bone Joint Surg Am. 1992; 74: 491-500
        • Roche C.
        • Angibaud L.
        • Flurin P.H.
        • Wright T.
        • Fulkerson E.
        Anatomic validation of an anatomic shoulder system.
        Bull Hosp Jt Dis. 2006; 63: 93-97
        • Harryman D.T.
        • Sidles J.A.
        • Harris S.L.
        • Lippitt S.B.
        • Matsen F.
        The effect of articular conformity and the size of the humeral head component on laxity and motion after glenohumeral arthroplasty. A study in cadavera.
        J Bone Joint Surg. 1995; 77: 555-563
        • Nyffeler R.W.
        • Sheikh R.
        • Jacob H.A.
        • Gerber C.
        Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study.
        J Bone Joint Surg Am. 2004; 86–86A: 575-580
        • Malavolta E.A.
        • Assunçao J.H.
        • Pagotto R.A.
        • et al.
        The rotation of the humeral head does not alter the radiographic evaluation of the head-shaft angle.
        J Shoulder Elbow Surg. 2016; 25: 543-547
        • Jeong J.
        • Bryan J.
        • Iannotti J.P.
        Effect of a variable prosthetic neck-shaft angle and the surgical technique on replication of normal humeral anatomy.
        J Bone Joint Surg [Am]. 2009; 91-A: 1932-1941
        • Goldberg R.W.
        • Williamson D.F.
        • Hoven H.A.
        • Liu R.W.
        Humeral version and neck-shaft angle correlated with demographic parameters in a study of 1104 cadaveric humeri.
        J Shoulder Elbow Surg. 2020; 29: 1236-1241
        • Solonen K.A.
        • Vastamaki M.
        Osteotomy of the neck of the humerus for traumatic varus deformity.
        Acta Orthop Scand. 1985; 56: 79-80
        • Takase K.
        • Yamamoto K.
        • Imakiire A.
        • Burkhead Jr., W.Z.
        The radiographic study in the relationship of the glenohumeral joint.
        Journal of Orthopedic Research. 2004; 22: 298-305
        • Longo U.G.
        • Gulotta L.V.
        • De Salvatore S.
        • et al.
        The role of humeral neck-shaft angle in reverse total shoulder arthroplasty: 155° versus <155°-A systematic review.
        J Clin Med. 2022; 11 (3641): 1-16
        • Gobezie R.
        • Shishani Y.
        • Lederman E.
        • Denard P.J.
        Can a functional difference be detected in reverse arthroplasty with 135° versus 155° prosthesis for the treatment of rotator cuff arthropathy: a prospective randomized study.
        J Shoulder Elbow Surg. 2019; 28: 813-818
        • Werner B.
        • Chaoui J.
        • Walch G.
        The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty.
        J Shoulder Elbow Surg. 2017; 26: 1726-1731
        • Oh J.H.
        • Shin S.J.
        • McGarry M.H.
        • Scott J.H.
        • Heckmann N.
        • Lee T.Q.
        Biomechanical effects of humeral neck-shaft angle and subscapularis integrity in reverse total shoulder arthroplasty.
        J Shoulder Elbow Surg. 2014; 23: 1091-1098
        • Middernacht B.
        • Tongel A.V.
        • De Wilde L.
        A critical review on prosthetic features available for reversed total shoulder arthroplasty.
        BioMed Res Int. 2016; : 1-9https://doi.org/10.1155/2016/3256931
        • Wirth M.A.
        • Ondrla J.
        • Southworth C.
        • Kaar K.
        • Anderson B.C.
        • Rockwood C.A.
        Replicating proximal humeral articular geometry with a third-generation implant: a radiographic study in cadaveric shoulders.
        J Shoulder Elbow Surg. 2007; 16: 111-116
        • McPherson E.J.
        • Friedman R.J.
        • An Y.H.
        • Chokesi R.
        • Dooley R.L.
        Anthropometric study of normal glenohumeral relationships.
        J Shoulder Elbow Surg. 1997; 6: 105-112