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Radiographic Study of Humeral Stem in Shoulder Arthroplasty After Lesser Tuberosity Osteotomy or Subscapularis Tenotomy

May 23, 2018 | Surgery
Robert Mason, MD ; Taylor Buckley, MD ; Richard Southgate, MD ; Gregg Nicandri, MD ; Richard Miller, MD ; Ilya Voloshin, MD
Author and Disclosure Information

Authors’ Disclosure Statement: Dr. Voloshin reports that he is a paid consultant for Zimmer Biomet, Smith & Nephew, Arthrex, and Arthrosurface. The other authors report no actual or potential conflict of interest in relation to this article.

Dr. Mason and Dr. Southgate are Orthopaedic Residents, and Dr. Nicandri and Dr. Miller are Associate Professors, Department of Orthopaedics and Rehabilitation, University of Rochester, Rochester, New York. Dr. Buckley is an Orthopedic Surgeon, Northern Rockies Orthopedics; and an Orthopedic Surgeon, Saint Patrick’s Hospital, Community Medical Center, Missoula, Montana. Dr. Voloshin is Professor of Orthopedics; Chief, Shoulder and Elbow Division; and Team Physician, Rochester Knighthawks NLL Lacrosse, Rochester Rattlers MLL Lacrosse Shoulder, Elbow, Knee Surgery-Sports Medicine, Department of Orthopaedics and Rehabilitation, University of Rochester, Rochester, New York.

Address correspondence to: Ilya Voloshin, MD, University of Rochester Medical Center, 601 Elmwood Avenue, Box 665, Rochester, NY 14625 (tel, 585-276-3106; fax, 585-276-2550; email, Ilya_Voloshin@urmc.rochester.edu).

Am J Orthop. 2018;47(5). Copyright Frontline Medical Communications Inc. 2018. All rights reserved.

Robert Mason, MD Taylor Buckley, MD Richard Southgate, MD Gregg Nicandri, MD Richard Miller, MD Ilya Voloshin, MD . Radiographic Study of Humeral Stem in Shoulder Arthroplasty After Lesser Tuberosity Osteotomy or Subscapularis Tenotomy. Am J Orthop.

May 23, 2018

TAKE-HOME POINTS

  • LTO and ST remain viable options for takedown of the subscapularis.
  • No difference exists in subsidence, lucent lines, and posterior subluxation on radiographic evaluation between LTO and ST.
  • No clinically significant difference exists between outcome scores of patients with either technique.
  • HAD was statistically significant but not clinically relevant between the 2 techniques.
  • Results from the study do not apply to metaphyseal fitting stems, only diaphyseal fitting stems. 

Posterior subluxation is indicated by a value >65%, a centered head is between 35% and 65%, and anterior subluxation is indicated by a value <35% (Figure 4).3 

The subluxation index was calculated using the method outlined by Gerber and colleagues3 using the axillary view radiograph (Figure 4). The midpoint of the glenoid was identified. Then, a perpendicular line (line z) was drawn projecting from the midpoint of the glenoid through the humeral head. Two lines were then drawn in an anterior-to-posterior direction on the humeral head. The first line (measurement A) was drawn from the posterior cortex to the previous perpendicular line (line z). The second line (measurement B) was drawn from the posterior to the anterior cortex. Measurements A and B should be calculated at the same height on the humeral head, roughly at the anatomic neck. The subluxation index is then calculated as A/B × 100. This was calculated both preoperatively and postoperatively.

The humeral stems were evaluated for loosening by assessing for lucency on final radiographic follow-up films. These were evaluated in a zonal fashion as demonstrated by Sanchez-Sotelo and colleagues4 and in Figure 5. 

The humeral stem-bone interface was evaluated in 8 radiographic zones. A lucency was not considered significant unless >2 mm. The zone of lucency was then determined for any significant lucencies. Zones 1 and 7 were at the level of the neck component, zones 2 and 6 were at the proximal half of the stem component, and zones 3 and 5 were at the distal half of the stem component. Zone 8 was noted directly inferior to the humeral head prosthesis.4

FUNCTIONAL OUTCOME EVALUATION

Before clinical evaluation, each study patient completed the Western Ontario Osteoarthritis of the Shoulder (WOOS) index; the Disabilities of the Hand, Arm and Shoulder (DASH) questionnaire, and the pain and function sections of the Constant score. The functional outcomes scores were captured postoperatively from October to November 2011. The WOOS is a validated outcome measure specific to osteoarthritis of the shoulder and has been used in prior studies evaluating outcomes of TSA.5-7 Previous studies have determined that the minimal clinically important difference for the WOOS score is 15 on a normalized 0 to 100 scale (100 being the best). The DASH score is a validated outcome measure for disorders of the upper extremity but is not specific to osteoarthritis of the shoulder.8 The Constant score is a validated outcome measure for a number of shoulder disorders, including TSA.9,10

STATISTICAL ANALYSIS

Statistical analyses were completed by a trained biostatistician. A power analysis was calculated using the noninferiority test to determine if adequate data had been obtained for this study. This was calculated by using previously accepted data demonstrating a statistically significant difference for subsidence and HAD. The data from these studies were used to make assumptions regarding accepted standard deviations and noninferiority margins, as calculated from the mean values of the 2 groups analyzed in each respective study.4,11 This analysis demonstrated power of 0.97 and 0.85 for the subsidence and HAD, respectively, given the current sample sizes. Intraclass coefficients were calculated to evaluate the measurements obtained during the radiographic analysis to determine the interrater agreement. Two samples’ t tests were calculated for the variables analyzed, along with P values and means.

RESULTS

DEMOGRAPHICS

A total of 51 consecutive patients were retrospectively selected for analysis. Of these, 16 patients were excluded from the study because they had <9 months of radiographic follow-up and were unavailable for further follow-up evaluation. Of the remaining 35 patients available for analysis, 4 patients had bilateral TSA, providing 39 shoulders for evaluation. Demographic characteristics of the study cohort are reported in Table 1.

Table 1. Demographic Characteristics    
 Tenotomy (n = 24) Osteotomy (n = 15) P-value
Age 68.2 [7.4] 70.2 [7.1] 0.46
Follow-up 20.6 [11.5]18.5 [6.25] 0.94
Females 7 (29%) 6 (40%) 0.58
Dominant shoulder 14 (58%) 8 (53%) 0.81
Primary Diagnosis   
Osteoarthritis 22 (92%) 15 (100%)  
Rheumatoid arthritis 2 (8%) 0 (0%)  

  Fifteen patients underwent LTO, and 24 underwent ST. One patient underwent a tenotomy of the right shoulder and LTO of the left shoulder. Three LTOs were performed by the surgeon who primarily performed ST, owing to potential benefits of LTO. He eventually returned to his preferred technique of ST because of surgeon preference. Three ST procedures were completed by the surgeon who typically performed LTO at the start of the series prior to establishing LTO as his preferred technique. There was no significant difference between the study populations in terms of age, follow-up, male-to-female ratio, hand dominance, and primary diagnosis of osteoarthritis vs rheumatoid arthritis.

Continue to: There was no significant difference...

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