🦵 Achilles Tendon Repair Technique Simulator

Recognizing Achilles Rupture — Mechanism, Exam, and the Thompson Test

Acute Achilles tendon rupture typically occurs during forceful eccentric loading of a dorsiflexed ankle — a sudden push-off during sprinting, jumping, or a lunge, classically in an active adult in their 30s–50s (the so-called "weekend warrior"). The diagnosis is overwhelmingly clinical: a palpable defect and a positive Thompson test identify the vast majority of cases without imaging, though ultrasound or MRI resolve equivocal presentations.

• 2–6cm: Typical gap location (proximal to calcaneal insertion)
• ~96%: Thompson test sensitivity (squeeze calf, no plantarflexion = rupture)
• 30–50yo: Peak incidence (recreational athletes, "weekend warrior")
• up to 25%: Missed on first visit (when exam is incomplete)

Clinical presentation and confirmatory examination

Mechanism of injury: the classic history is a sudden, forceful eccentric contraction of the gastrocnemius-soleus complex against a dorsiflexed ankle — pushing off to sprint, jumping and landing awkwardly, or a sudden lunge in racquet sports. Patients frequently describe feeling as though they were struck or kicked in the back of the calf/ankle, sometimes with an audible pop, followed by immediate pain and difficulty bearing weight.

Inspection and palpation: • A visible and palpable gap or defect is typically found 2–6cm proximal to the calcaneal insertion — this is the tendon's relative watershed (hypovascular) zone, the most common rupture site • Swelling and ecchymosis develop over the posterior ankle within hours • Resting tension is decreased: with the patient prone and knees flexed, the injured ankle rests in a more dorsiflexed position than the uninjured side

Thompson (Simmonds) test: • Patient prone, feet hanging off the exam table edge, examiner squeezes the mid-calf • Normal: the squeezed gastrocnemius-soleus complex produces passive ankle plantarflexion via the intact tendon • Positive test (rupture): no plantarflexion occurs — the calf muscle contracts against a discontinuous tendon • Sensitivity and specificity both exceed 90–96% when performed correctly, making it the single most useful bedside maneuver

Matles test: patient prone with knees flexed to 90°; normal ankle falls into slight plantarflexion, while a ruptured side falls into neutral or dorsiflexion — a useful confirmatory sign.

Imaging: plain radiographs mainly exclude avulsion fracture; ultrasound (dynamic, low-cost, can assess gap distance with the ankle in various positions) or MRI (best for chronic/equivocal presentations, partial tears, or preoperative planning) confirm the diagnosis when clinical exam is ambiguous — roughly 20–25% of acute ruptures are missed on initial presentation when a thorough exam including the Thompson test is not performed.

Operative vs Nonoperative — Choosing the Path After Diagnosis

The historical dichotomy between "surgery for athletes, casting for everyone else" has evolved considerably. Modern functional rehabilitation protocols — early controlled range of motion and progressive weight-bearing in a hinged boot, rather than prolonged rigid immobilization — have narrowed the rerupture-rate gap between nonoperative and operative treatment, shifting the decision toward shared decision-making based on patient-specific factors.

• ~10–12%: Historic nonop rerupture (with rigid cast immobilization)
• ~2–5%: Historic operative rerupture (across repair techniques)
• ~2.5–5%: Modern functional nonop rerupture (with accelerated rehab protocols)
• <2 weeks: Acute repair window (delayed repair is more complex)

Factors driving the operative vs nonoperative decision

Landmark evidence shift: earlier trials comparing operative repair to nonoperative treatment with rigid cast immobilization consistently favored surgery, with rerupture rates around 10–12% for nonoperative vs 2–5% for operative care. However, subsequent randomized trials (e.g., Willits et al., JBJS 2010) comparing operative repair to nonoperative treatment using an accelerated functional rehabilitation protocol — early protected range of motion and progressive weight-bearing rather than prolonged casting — found comparable rerupture rates between the two groups (roughly 2.5–5% in both arms), fundamentally changing practice patterns.

Factors favoring operative repair: • Competitive or high-demand athletes seeking maximal strength/power recovery and fastest return to sport • Delayed presentation (>2 weeks), where tendon retraction makes nonoperative healing less reliable • Large gap distance (>5–6cm even acutely) that may not appose adequately with the ankle in plantarflexion alone • Patient preference after being counseled on trade-offs

Factors favoring nonoperative (functional) treatment: • Lower-demand or sedentary patients • Higher surgical risk (diabetes, peripheral vascular disease, smoking, immunosuppression) where wound complications are a major concern • Elderly patients, where functional rehab avoids surgical risk with acceptable functional outcomes

Timing: acute ruptures (<2 weeks from injury) are far more amenable to either treatment pathway. Delayed or chronic ruptures (>4–6 weeks), where the tendon has retracted and the gap has filled with scar tissue, typically require operative reconstruction with tendon transfer (commonly flexor hallucis longus, FHL) or graft augmentation rather than simple end-to-end repair.

The Willits et al. 2010 randomized trial fundamentally shifted practice: when both operative and nonoperative patients follow the same accelerated functional rehabilitation protocol (early motion, progressive weight-bearing), rerupture rates converge to roughly 2.5–5% in both groups — meaning the choice of surgery vs no surgery matters far less than the choice of rehabilitation protocol.

Open, Percutaneous, or Mini-Open — Selecting the Surgical Approach

When operative repair is chosen, three broad technique families are available, each trading off wound complication risk, nerve injury risk, and the surgeon's ability to directly visualize and control tendon apposition. The choice is influenced by surgeon experience, tendon gap size, and patient tissue quality.

• 5–10%: Open repair wound complications (infection/dehiscence risk)
• 0–13%: Percutaneous sural nerve injury (technique-dependent, jig-guided lowers risk)
• ~3–5cm: Mini-open incision length (balances visualization & soft-tissue risk)
• ~1–2%: Percutaneous wound complications (lowest of the three approaches)

Comparing open, percutaneous, and mini-open repair

Open repair: • Standard posteromedial longitudinal incision (medial to the tendon, avoiding the sural nerve laterally) providing full direct visualization of both tendon stumps • Allows precise debridement of frayed tendon ends, direct suture placement, and confident restoration of length/tension • Lowest rerupture rate among the three approaches due to the most secure, directly-visualized repair • Highest wound complication rate (~5–10%): the posterior ankle has relatively poor soft-tissue coverage and blood supply, making infection and wound dehiscence the main drawback, particularly in smokers, diabetics, and patients with vascular disease

Percutaneous repair: • Multiple small stab incisions (a few millimeters each) along the tendon, with sutures passed using techniques such as the Ma-Griffith method or a purpose-built jig (Achillon or PARS — Percutaneous Achilles Repair System) • Minimizes soft-tissue disruption, substantially lowering wound complication rates to roughly 1–2% • Historical drawback: earlier freehand percutaneous techniques carried sural nerve injury rates reported as high as 13%, since the nerve's course near the lateral aspect of the tendon cannot be directly visualized through stab incisions; modern jig-guided systems that protect the nerve during suture passage have reduced this risk to low single digits or lower

Mini-open (limited-open) repair: • A short (~3–5cm) incision that allows partial direct visualization of tendon apposition while limiting soft-tissue disruption compared to a full open approach • Intended to capture much of the wound-complication benefit of percutaneous technique while retaining more of the apposition confidence of open repair • Increasingly popular as jig systems have matured, often considered a reasonable middle-ground default in many modern practices

Selection in practice: surgeon experience and familiarity with a given jig system often drives technique choice as much as patient factors; all three approaches, in experienced hands, achieve good functional outcomes with rerupture rates in the low single digits.

Krackow Stitches and Restoring Correct Tendon Tension

Whichever approach is used to access the tendon, the mechanical strength of the repair depends on the core suture construct and, just as critically, on restoring the tendon's native resting length and tension — a subtle but decisive technical detail that governs postoperative calf strength and gait symmetry.

• Krackow: Preferred core stitch (locking loop, high pull-out strength)
• #0–2 nonabsorbable: Suture size/material (e.g. braided polyethylene (FiberWire))
• contralateral leg: Tension reference (knee flexed 90°, Silfverskiold-guided)
• FHL transfer: Chronic case augmentation (or plantaris/graft for large defects)

Core suture constructs and tensioning technique

Core stitch options: • Krackow locking-loop stitch: a series of locking loops passed through the tendon substance on each side of the rupture, which resist suture pull-through under tension better than simple running stitches — the most widely favored core stitch in modern Achilles repair for its superior biomechanical strength • Bunnell stitch: a crisscrossing intratendinous suture pattern, an older alternative with somewhat lower pull-out strength than Krackow • Kessler stitch (and modified Kessler): a grasping core suture technique borrowed from hand tendon repair, sometimes used as an alternative or in combination

Suture material and size: typically a size 0 to 2 nonabsorbable braided suture (e.g., FiberWire or similar high-strength polyethylene-core material) is used for the core stitch, given the substantial tensile loads the Achilles transmits during gait and push-off. An epitendinous running suture (a fine absorbable or nonabsorbable suture along the tendon surface) is added to smooth the repair site and provide supplemental strength.

Restoring resting tension — the critical, easily-overlooked step: • Overtightening the repair shortens the musculotendinous unit, weakening push-off power and altering gait • Undertightening leaves the tendon too long/lax, also compromising calf strength and increasing perceived weakness • Standard technique: with the patient prone and both knees flexed to 90°, the surgeon compares the resting ankle cascade of the operative side to the uninjured contralateral ankle (Silfverskiold-guided or "resting tension" technique) before final suture tying, aiming to match the two sides as closely as possible

Augmentation for chronic or revision cases: when tendon ends have retracted and cannot be approximated primarily (typically ruptures presenting >4–6 weeks after injury), flexor hallucis longus (FHL) tendon transfer is the most common augmentation, providing a vascularized local tendon to bridge the defect and contribute active plantarflexion power; plantaris tendon weave or synthetic/allograft augmentation are alternative options for very large defects.

Accelerated Functional Rehabilitation and Long-Term Outcomes

Modern Achilles rehabilitation has moved decisively away from prolonged rigid casting toward accelerated functional protocols: early protected motion and progressive weight-bearing that both reduce rerupture risk relative to old immobilization-only regimens and speed return to activity, while a modest long-term strength deficit remains a well-documented, largely unavoidable feature of recovery.

• 6–8 weeks: Full weight-bearing (progressive wedge removal from boot)
• 12–16 weeks: Return to running (after strengthening phase)
• 4–6 months: Return to sport (sport- and position-dependent)
• 10–30%: Long-term calf strength deficit (persists even in good outcomes)

Accelerated functional rehabilitation protocol and outcome measures

Weeks 0–2: controlled ankle motion (CAM) boot with heel wedges holding the ankle in slight plantarflexion, non-weight-bearing to touch-down weight-bearing depending on surgeon protocol; early gentle active-assisted range of motion within a protected arc may begin as early as 1–2 weeks in many accelerated protocols.

Weeks 2–6: progressive weight-bearing as tolerated in the boot, with heel wedges removed incrementally (typically one wedge every 1–2 weeks) to gradually restore neutral ankle dorsiflexion; physical therapy focuses on edema control, scar mobilization, and protected range of motion.

Weeks 6–8: transition out of the boot into supportive footwear once full weight-bearing is comfortable and clinical exam confirms adequate healing; formal strengthening phase begins, starting with isometric and light resistance exercises for the gastrocnemius-soleus complex.

Weeks 8–12: progressive resistance strengthening, proprioceptive/balance training, and gait retraining; double-leg then single-leg heel raises are a key strength milestone tracked throughout this phase.

Weeks 12–16: return to running typically permitted once single-leg heel-raise capacity and pain-free full range of motion are demonstrated; sport-specific agility drills introduced.

Months 4–6: return to competitive sport, guided by achieving calf strength and hop-test symmetry within an acceptable range (commonly targeting >85–90% of the contralateral limb) rather than by time alone.

Outcome measures and long-term findings: • Achilles Tendon Total Rupture Score (ATRS): a validated 10-item patient-reported outcome measure assessing symptoms and functional limitations; most patients achieve substantial improvement by 12 months, though scores may continue to improve up to 2 years • Rerupture rate: approximately 2–5% after surgical repair with modern functional rehabilitation, similar rates now reported with nonoperative functional treatment in appropriately selected patients • Persistent calf strength/endurance deficit: even in patients with excellent subjective outcomes, isokinetic testing frequently reveals a 10–30% plantarflexion strength deficit compared to the uninjured leg at 1 year and sometimes persisting beyond, attributed to musculotendinous unit lengthening and incomplete muscle recovery • Deep vein thrombosis: a recognized risk during the immobilization/reduced-weight-bearing period, with some protocols incorporating prophylaxis in higher-risk patients

The single biggest advance in Achilles rehabilitation over the past two decades is not a change in surgical suture technique but a change in postoperative philosophy: accelerated functional rehabilitation with early controlled motion has simultaneously reduced rerupture rates and shortened recovery time compared to the traditional 6-8 week rigid cast immobilization it replaced.