Overview
In situ fixation stabilizes the capital femoral epiphysis and prevents further displacement across the physis. In a stable SCFE, a single centrally positioned cannulated screw is the source's preferred treatment. The immediate objective is stable fixation without joint penetration or compromise of femoral head blood supply, rather than forceful correction of the existing deformity (Tachdjian, Chapter 15).
This guide addresses stable slips. An unstable slip is a distinct high-risk condition; the free-leg tabletop maneuvers described here should not be transferred to that setting.
Assessment and Indications
Determine clinical stability before choosing positioning and imaging maneuvers. The Loder classification uses the ability to bear weight, with or without crutches; clinical classification can underestimate actual physeal instability.
Once SCFE is recognized, prevent further weight bearing and arrange prompt definitive treatment. A previously mild slip can displace further before stabilization.
Review AP and appropriate lateral imaging of both hips, the severity and direction of displacement, and the status of the opposite physis.
Document symptoms, motion and associated clinical concerns. Fixation prevents progression but may not eliminate impingement caused by residual deformity.
Discuss the risks of osteonecrosis, chondrolysis, progression, joint penetration and contralateral slip, together with the need for surveillance until maturity.
(Tachdjian, Chapter 15.)
Equipment and Positioning
Setup | Use and limitations |
|---|---|
Radiolucent tabletop, leg prepared free | Appropriate for a clinically stable slip; permits controlled changes in hip position for imaging and final screw assessment. |
Fracture table | Allows controlled positioning with fluoroscopic AP and lateral imaging; minimize manipulation and avoid excessive internal rotation. |
Fluoroscopy | Must clearly define the epiphysis and subchondral margin in more than one projection before drilling. |
Cannulated fixation system | Use an appropriate large-core screw and stout guidewire with reliable measuring, drilling and extraction instruments. |
Tachdjian describes 6.5- or 7.3-mm screw systems for the fracture-table method. Implant choice, thread length and available epiphyseal purchase must be planned for the individual anatomy. The source favors long-thread or fully threaded designs for fixation and possible later extraction (Chapter 15).
Surgical Technique
Plan the Trajectory
Before preparing the limb, verify that the femoral head and physis can be seen adequately on AP and lateral fluoroscopy.
Use a wire on the skin to mark the intended trajectory in both projections.
Recognize that the epiphysis usually lies posteriorly relative to the neck. A screw directed centrally into the head therefore starts at the anterior base of the femoral neck and travels posteriorly.
Aim as centrally as possible in the epiphysis and approximately perpendicular to the physis while avoiding a starting point that produces anterior screw-head impingement.
With more severe deformity, reconcile central epiphyseal purchase with an entry at or lateral to the intertrochanteric line as described in the source. Do not judge the starting point from the AP image alone.
(Tachdjian, Chapter 15.)
Guidewire Placement
Make a small skin incision and bluntly open the fascia to prevent soft tissues from deflecting the wire.
Position the wire at the planned bony entry and verify location and orientation on both views.
Advance under repeated fluoroscopic control toward the center of the capital epiphysis without entering the joint.
When a stable hip is repositioned for the lateral view, protect the guidewire from bending against the fascia. If the trajectory is unsuitable, correct it deliberately rather than accepting eccentric purchase.
Confirm the final wire position in orthogonal projections and measure the required screw length.
(Tachdjian, Chapter 15, Fig. 15.11.)
Drilling and Screw Insertion
Drill and tap as required by the selected system, monitoring the wire so it neither advances into the joint nor withdraws from its channel.
Insert the cannulated screw with sufficient threads across the physis for epiphyseal fixation. Tachdjian describes confirming approximately four or five threads within the epiphysis.
Keep the screw centrally positioned. Eccentric placement raises the risks of inadequate fixation and joint penetration.
Reassess the subchondral margin in multiple projections. Fluoroscopy can overestimate the apparent distance from the screw tip to the joint, particularly on the AP view.
Remove the wire only after satisfactory fixation and length are confirmed.
(Tachdjian, Chapter 15.)
Final Dynamic Assessment
After fixation of a stable slip, gently move the hip through the permitted arc while obtaining additional fluoroscopic views.
Alternatively, rotate the fluoroscope through successive projections to assess the relationship of the screw to the entire head.
Confirm absence of joint penetration, adequate epiphyseal thread purchase and no unacceptable screw-head impingement.
Close the small wound and document the final screw position and the condition of the opposite hip.
(Tachdjian, Chapter 15.)
Pearls and Pitfalls
Stability determines handling: a freely manipulated tabletop technique is reserved for stable slips.
Two planes are essential: a satisfactory AP appearance can conceal inadequate epiphyseal purchase or penetration elsewhere.
Protect the guidewire: bending can jam the cannulated instruments or lead to loss of control.
Do not force reduction: the aim of in situ fixation is to stabilize the existing relationship.
Plan the entry point: a very anterior screw head can create later impingement even with a central tip.
More implants are not automatically better: a single well-placed screw usually stabilizes a stable slip; additional implants also add opportunities for complication.
(Tachdjian, Chapter 15.)
Postoperative Care
The source permits protected partial weight bearing with crutches when comfortable, commonly within 24 hours, and continues crutches for approximately 6 weeks. It describes return to athletic activity around 3 months after clinical recovery. These intervals apply to the described fixation pathway and do not replace assessment of symptoms, stability and healing (Tachdjian, Chapter 15).
Continue clinical and radiographic review at approximately 3–6-month intervals until skeletal maturity to monitor the treated hip and detect a contralateral slip. New pain, motion loss or recurrent limp requires reassessment; unilateral fixation does not protect the opposite hip (Tachdjian, Chapter 15).
Complications
Joint penetration by the wire, drill or screw, potentially causing cartilage injury or chondrolysis.
Osteonecrosis, with risk strongly influenced by slip stability and treatment-related vascular insult.
Progression from inadequate fixation or insufficient epiphyseal purchase.
Residual femoroacetabular impingement from the deformity or prominent screw head.
Implant extraction difficulty and later contralateral slipping.
(Tachdjian, Chapter 15.)
References
Podeszwa D. Slipped capital femoral epiphysis. In: Herring JA, ed. Tachdjian's Pediatric Orthopaedics: From the Texas Scottish Rite Hospital for Children. 6th ed. Elsevier; 2022. Chapter 15, stability classification, pp. 581–583; in situ fixation and postoperative management, pp. 589–593, Fig. 15.11 and Plate 15.1.