Soft Tissue Balancing

SOFT TISSUE EXPOSURE/BALANCING

Mr M Thomas, Consultant Orthopaedic Surgeon, Heatherwood Hospital, UK
Presented at: International Shoulder Symposium - Leysin, Switzerland - 4-5 March 2005

“Shoulder arthroplasty, more than arthroplasties of other joints, demands the preservation and rehabilitation of the soft tissue. Treatment of the soft tissue is as important as the orientation and fixation of the components”

Charles S Neer

With this in mind every shoulder arthroplasty including surface replacement requires:
         
- Release of scar tissue and contractures
- Repair of damaged soft tissue structures if possible (eg rotator cuff)
- Proper sizing and placement of components

The surgeon must restore enough soft tissue balance so the unconstrained implant can be moved while remaining stable. The soft tissue procedures required to achieve this includes pectoralis major release, Subscapularis lengthening and capsular releases. With surface replacement arthroplasty the sizing of the humeral head is less of a problem than with modular stemmed implants when over sizing results in a stiff overstuffed joint whilst under sizing can result in instability.

The cause of the Glenohumeral arthritis predicts the bony and soft tissue abnormality

In osteoarthritis the bony abnormality may comprise of:
- Circumferential humeral head osteophytes
- Glenoid osteophytes
- Posterior glenoid wear
- Posterior subluxation of the humeral head
The soft tissue abnormality is:
- Posterior capsular stretching
- Anterior contracture

The surgical requirements in osteoarthritis therefore include:
- Anterior capsular release
-  Subscapularis lengthening
-  Correction of asymmetric glenoid erosion
- ?? Glenoid resurfacing

In rheumatoid arthritis the bony abnormality may comprise of:
- Medial glenoid wear which is superoanterior and maybe extensive
- ? Coracoid erosion
- Humeral head erosion
The soft tissue abnormality is:
-  cuff tears in 33%
- Cuff weakness and superior humeral head migration

The surgical requirements in rheumatoid arthritis therefore include:
- ? Cuff repair
- ? Anterior release and subscapularis lengthening
- ? Circumferential capsular release
- ? Glenoid replacement possible / desirable

In post traumatic arthritis the bony abnormality may comprise of:
- Distortion of normal anatomy due to fracture malunion
- ? Avascular necrosis humeral head
The soft tissue abnormality is:
- Extensive scarring from previous trauma
- ? Heterotopic bone within soft tissues
- ? Significant anterior and posterior contracture

The surgical requirements in post traumatic arthritis therefore include:
- Subscapularis lengthening
- Extensive capsular release
- ? Retraction greater tuberosity – osteotomy needed
 
In post dislocation arthritis the bony abnormality may comprise of:
- Uneven glenoid wear
- Humeral head defect
The soft tissue abnormality is:
- Over tight anterior structures from previous surgery
- Subscapularis and capsular contracture
- ? Subluxation opposite direction to original surgery

The surgical requirements in post dislocation arthritis therefore include:
- Lengthening subscapularis
- ? Glenoid bone deficiency
- Extensive capsular release
- ?? Instability of components

In rotator cuff arthropathy the bony abnormality may comprise of: 
- Erosion of superior glenoid, coracoid and acromion
The soft tissue abnormality is:
- Cuff weakness – vertical subluxation humeral head contained by the coracoacromial arch
- Usually massive cuff tear – longstanding and irreparable
- Remaining cuff thin, friable and difficult to mobilise

The surgical difficulties in cuff tear arthropathy are:
- Cuff deficiency makes balancing virtually impossible
- Centering of head is not possible
- Maintain some stability by retaining Coracoacromial arch

Successful soft tissue balancing will give following movement intraoperatively at the end of the procedure which is the minimum required adequate shoulder function.
 - 30 degrees of external rotation
- Hand to opposite axilla
- Hand to head/hair
- Hand to perineum
The movement achieved on the operating table will also never be bettered post operatively.