Is posterior reach (reaching behind the back) severely limited after reverse total shoulder arthroplasty, and does the patient require range‑of‑motion (ROM) exercises to improve it?

Posterior Reach After Reverse Total Shoulder Arthroplasty

Yes, reaching behind the back (internal rotation) is severely and persistently limited after reverse total shoulder arthroplasty, and ROM exercises have not been proven to meaningfully improve this specific motion.

The Reality of Internal Rotation Deficits

Internal rotation (IR) is the most compromised motion after reverse TSA and shows the poorest recovery trajectory compared to all other shoulder movements. Patients achieve only 48.4% of contralateral internal rotation capacity at final follow-up 1. This is a fundamental biomechanical consequence of the reverse prosthesis design, not simply a rehabilitation issue.

Specific Functional Limitations

Activities of daily living that require internal rotation demonstrate consistently poor recovery rates 1:

• Only 36.4% of patients can wash their back at final follow-up
• Mean scores below 2.0 (out of 3.0) for:
  • Washing the opposite shoulder
  • Washing the opposite axilla
  • Using a back pocket
  • Managing toilet hygiene
  • Washing the back

These deficits persist despite otherwise satisfactory clinical outcomes in pain relief and forward elevation.

The Biomechanical Explanation

The reverse TSA design fundamentally alters shoulder mechanics 2. The construct moves the center of rotation medial and distal, allowing the deltoid to serve as the main stabilizer. However, this same design change that improves forward elevation inherently compromises internal rotation because:

• The rotator cuff is deficient or absent (the primary indication for reverse TSA)
• Glenohumeral contribution to rotation remains reduced
• Motion occurs predominantly through compensatory scapulothoracic movement 3
• Posterior cuff recruitment remains limited even postoperatively 3

Internal rotation does not reach preoperative status even at final follow-up, while forward elevation and external rotation recover within 6 months 1. This differential recovery pattern indicates a structural limitation rather than a rehabilitation deficit.

Evidence on ROM Exercises

The evidence regarding postoperative ROM exercises after reverse TSA is remarkably weak:

No Proven Benefit of Formal Physical Therapy

A multicenter randomized clinical trial directly compared structured home exercise programs versus active supervised physiotherapy after reverse TSA 4. There were no significant differences in patient-reported outcomes or ROM at final follow-up between groups. This suggests that intensive ROM exercises do not overcome the inherent biomechanical limitations of the reverse prosthesis.

Accelerated Rehabilitation Shows Non-Inferiority

A study of 357 consecutive reverse TSAs compared three rehabilitation protocols: 6 weeks immobilization, 3 weeks immobilization, and no immobilization with immediate activity 5. No statistically significant differences were observed in outcomes, ROM, or patient satisfaction between groups. The accelerated protocol (no immobilization) actually showed fewer postoperative complications.

Guidelines Acknowledge the Evidence Gap

The American Academy of Orthopaedic Surgeons guideline on shoulder arthroplasty explicitly states: "We are unable to recommend for or against physical therapy following shoulder arthroplasty" due to insufficient quality evidence 6. Similarly, they cannot recommend for or against specific timing of ROM exercises 7.

Clinical Implications

Set Realistic Expectations

Counsel patients preoperatively that internal rotation will remain limited, particularly for activities like reaching behind the back, fastening bras, or performing perineal hygiene. This is an expected outcome, not a complication.

ROM Thresholds for Functional Improvement

Recent evidence identifies specific ROM thresholds beyond which additional motion provides minimal improvement in patient-reported outcomes 8:

• Internal rotation to L1 vertebral level (IR score 4-5 points)
• Beyond this threshold, further IR gains show diminishing returns

Only 4.8% of reverse TSA patients achieve or exceed all ROM thresholds, highlighting the inherent limitations of this procedure.

Practical Rehabilitation Approach

Given the evidence:

1. Immediate mobilization is safe - no immobilization period is necessary 5
2. Home exercise programs are equivalent to formal PT for most patients 4
3. Focus rehabilitation efforts on forward elevation and external rotation, which show better recovery potential
4. Do not aggressively pursue internal rotation gains - the biomechanical design limits this motion regardless of therapy intensity

Common Pitfall to Avoid

Do not attribute poor internal rotation recovery to inadequate patient compliance with ROM exercises. This creates unrealistic expectations and patient dissatisfaction. The limitation is structural, not behavioral.

When to Consider Formal Therapy

While formal PT is not universally necessary 4, consider it for:

• Patients with preoperative stiffness (passive ER ≤0°), who show slower recovery over longer duration 9
• Complications such as adhesive capsulitis or deltoid dysfunction 2
• Patients requiring return to high-demand activities

However, even in these cases, do not expect normalization of internal rotation.