Chapter 15.

Repair & Grafting of Tendon

ANATOMY

HISTOLOGY AND BIOCHEMISTRY

PHYSIOLOGY OF TENDON NUTRITION

PHYSIOLOGY OF TENDON GRAFT HEALING

Intrinsic versus Extrinsic Healing

Revascularization of Graft

Tendon Gliding

CLINICAL TRANSPLANTATION

Technique

Donor Sites

Palmaris longus

Plantaris

Extensor digitorum longus

Flexor digitorum superficialis

Tendon Sheath reconstruction

Two-Stage Tendon Grafting

Vascularized Tendon transfers

EXPERIMENTAL TRANSPLANTATION

Allografts

Xenografts

ANATOMY

Tendon

Paratenon(fig 15-1)

① loose elastic multilayered structure

② connect tendon to the surrounding structure

③ filmy homogeneous material containing mucopolysaccharide component

→ facilitate gliding motion

④ drape over a mesotenon (paratenon의 일부)

: contains blood supply to the tendon

Palmar Bursa(fig 15-3)

① no structural support

② enclose the tendons and define pathway for the spread of infection

③ palmar fascia divided into

ⓐ radial palmar bursa : communicates with thumb

ⓑ ulnar palmar bursa : communicates directly only with flexor tendon sheath of little finger

Tendon Sheath

□ Function

① prevent bowstring - mechanical aid to flexion

② allow acute flexion at the IP joint

③ allow smooth tendon gliding

④ enclosed bursal environment - tendon nutrition

□ 2 cruciate ligament proximal to each IP joint : vincular vessel이 통과하는 곳

□ tendon nutrition after transplantation : diffusion through synovial fluid

Blood Supply

1. Forearm & proximal palm : mesotenon --> blood supply to tendon on deep surface in segmental fashion

2. Digit : two specific vincular(condensed mesentery)를 통해 IP joint의 proximal 쪽에서 deep side of flexor tendon으로 들어감

□ tendon substance 내에서는 collagen fiber에 평행한 longitudinal intrafascicular vascular pattern이 있음(tendon dorsal aspect에 집중)

HISTOLOGY AND BIOCHEMISTRY

1. Tendon composition

① collagen : 70% of dry weight, type I

- basic unit : fibril ( tropocollagen, macromolecules로 구성 )

- glycin(30%), proline and hydroxyproline

- fibril → fiber (300 □m)→ fasciculi

- cross-linking of macromolecule → tensile strength 제공

② ground substance

ⓐ glycosaminoglycan - composed amino acid & uronic acid

maturation, aggregation, cementing of collagen fiber, lubrication

ⓑ glycoprotein

ⓒ noncollagenous protein

③ elastin

④ tenocyte

⑤ associated blood vessels, nerves and lymphatics

2. Cellular histology : 3 distinct population of tendon

① epitenon cells	: thin cellular layer on the outer margin of tendon

② endotenon cell	: continuation of epitenon projection into tendon bundle

③ tenocyte	: sparsely distributed cells within tendon bundles

PHYSIOLOGY OF TENDON NUTRITION

□ Tendon nutrition

① perfusion : vascular supply

② diffusion : synovial fluid - tendon graft시 initial survival에 가장 중요

- vascular connection이 없을 경우 tendon healing에 필요한 영양공급을 diffusion에 의해 공급가능

- radioactive tracer material로 조사한 결과 diffusion이 perfusion보다 더욱 효과적으로 tracer를 tendon으로 이동시킴

PHYSIOLOGY OF TENDON GRAFT HEALING

Healing of tendon ends(3 phase) - after tendon transplantation

⑴ cellular phase - collagen synthesis와 관련된 세포의 증식과 이동

ⓐ fibrinous material과 granulation tissue(RBC, macrophage, inf cell포함)가 transplanted tendon과 recipient stump사이의 space로 이동

ⓑ epitenon cell 증식, repair site로 침투 → fibroblast로 transform

⑵ collagen synthesis phase : 6일째 시작 수주간 지속

ⓐ fibroblast 수 증가 ( 2주에 peak )

ⓑ 이 시기에 revascularization이 시작됨

⑶ remodelling phase : function에 가장 중요한 시기

ⓐ tendon union gains strength & peritendinous adhesions lose strength

ⓑ 8 weeks : adhesion between graft & peritendinous tissue are filmy(엷은 막모양) and loose해짐

ⓒ 9개월 : 정상과 비슷

Intrinsic versus Extrinsic Healing ( from where? collagen producing cells )

⑴ Intrinsic

동물실험 - peripheral adhesion이 없이 healing 진행

① epitenon(초기), endotenon(수일 후), tenocyte(2-3주 후 관여)

② tenocyte--(transform)--> tenoblast : produce neocollagen

③ epitenon cell migrates & initiate repair with phagocytosis

--(then)--> endotenon cell (collagen synthesis)

⑵ Extrinsic - extrinsic fibroblasts from tendon sheath (synovial lining cell )

실험 - tendon내의 fibroblast는 증식하나 collagen 합성기능이 없음

□ agents for healing & production of new collagen

ⓐ cells within tendon(tenocyte, endotenon)

ⓑ cells on the surface of tendon(epitenon)

ⓒ cells in the surrounding tissue(fibroblast)

Revascularization of Graft

avascular tendon graft - 9일째 cellular necrosis, collagen bundle간 cohesiveness소실

--> To survive! revascularization is essential

⑴ "primary" revascularization

ⓐ direct anastomosis with vessels in bed

ⓑ tendon graft in nonsheath area

⑵ "secondary" revascularization

ⓐ ingrowth of capillary & new vascular network 형성

ⓑ tendon graft with sheath

--> 8주 째 longitudinal microvascular system (both dorsal & volar site)

--> 16주 째 dorsal network만 가진 정상 pattern으로 변화

□ but! nonsheath tendon의 경우 16주 후에도 volar & dorsal intratendinous vessel이 존재

□ "Secondary" revascularization most likely ensures the survival of tendon grafts with sheaths.

□ initial survival: synovial fluid nutrition이 중요함

□ complete survival은 capillary ingrowth가 가장 중요하다.

Tendon Gliding

: tendon graft가 paratenon으로 싸여있으면 술 중 paratenon(source of proliferation of fibroblast & scar tissue)의 제거는 중요하며 이때 epitenon을 다치지 않게(술 후 adhesion감소) 조심스럽게 제거해야 한다.

CLINICAL TRANSPLANTATION

Technique

⑴ Incision

① digit : midaxial or volar zigzag incision

② wrist : ulnar direction으로, median n.의 palmar cutaneous br.를 피하여

⑵ Graft bed preparation

① tendon sheath open시 : membranous portion을 열고, annular pulley는 보존

② joint부위를 dissection시

: palmar plate의 volar side에 국한 → joint stiffness 방지

③ FDP를 distal 부위에서 절단시 1 cm stump를 남기고 자른다.

④ FDS stump가 PIP joint부위에 존재할 경우 제거하지 않는다.

- allow a smooth bed(adhesion방지) and provide a tenodesis effect(joint stabilize)

- PIP joint hyperextension시 tenodesis시행

⑤ lumbricalis m.을 adhesion으로부터 dissection 할 때 retraction된 profundus stump까지 모든 adhesion을 분리

--> "lumbrical-plus" finger(fig 15-9)를 방지하기 위해

⑥ ulnar side의 3 FDP tendon은 같은 muscle belly에서 나오므로 이중 한 개를 절단해도 retraction되지 않음

⑦ tendon graft시 recipient motor기능은 필수적(즉 myostatic contracture(+) 인 경우는 CIx)이며 35mm의 tendon excursion이 만족스러운 arc of motion을 위해 필요 <-- muscle unit에 passive stretch를 해봐서 check

⑦ pulley를 reconstruction이 필요한 경우는 silicone rod을 이용한 two staged reconstruction이 필요

⑧ tendon suture

a) proximal : Pulvertaft fishmouth weave technique(fig 15-10)

b) distal juncture is made by the tendon just volar to pulp,

securing it to the stump of the profundus, and suturing the

end to the nail plate

Donor sites

□ Ideal donor tendon의 특징

① always present

② consistent in all its dimension

③ sufficient length : to bridge completely defect at the recipient site

④ superficially located : for ease of access

⑤ not affect function of donor area

⑥ thin : enough for adequate revascularization

⑦ sufficiently strong : for its new task

□ Commonly used tendon

① palmaris longus

② plantais

③ EDL tendons(2, 3, 4th toes)

④ FDS

⑤ amputated digit의 undamaged tendon

⑴ Palmaris longus

가. Anatomy

① 위치 : FCR와 FCU사이의 forearm의 deep fascia의 바로 deep portion

② median nerve innervation(C6, C7)

③ dimension : length: 10-12cm, width: 3-5cm, thickness: 1-2mm

④ insertion

① volar aspect of flexor retinaculum

② central part of palmar aponeurosis

⑤ palmaris longus와 혼동하기 쉬운 tendon : FCR

⑥ 잘 보이는 자세 : thumb과 little finger를 강하게 opposition

wrist를 slight flexion

나. Possible anomalies

① one of the most variable muscle

② agenesis : 20.9% of limbs

③ absence of palmaris did not predispose to absence of plantaris

다. 장점

① excellent access

② no permanent functional sequele of donor site

③ not thick : adequate vascularization

라. 단점 : long flexor tendon replacement graft를 하기엔 짧다.

(except little finger & thumb)

⑵ Plantaris

가. Anatomy

① vestigial muscle

② origin: lower part of lateral supracondylar line and oblique popliteal lig

③ insertion: calcaneus with Achilles tendon

④ tibial nerve innervation(S1,S2)

나. Technique of removal

① incision(fig 15-14)

longitudinal incision of approximately 2 - 3 cm anterior to the Achilles tendon on the medial aspect of the ankle region,

about 1 to 2 fingerbreaths proximal to the most proximal part of the calcaneus

② Achilles tendon의 accessory slip과 구분해야함

: paratenon(-), traction시 Achilles tendon movement(+)

③ full knee extension : tendon의 deep structure damage 방지

다. Possible anomalies

① absence: 18.2 %

② Achilles tendon에 insert : 60%

direct calcaneus insertion : 32%

라. 장점

① long : long flexor tendon replacement graft에 적합, two short graft

□ 3rd finger tip에서 wrist까지 tendon graft요구시 - plantaris! 사용

② not affect function of limb

③ adequate strength for flexor tendon replacement

④ not thick : revascularization 문제 없음

⑤ 2 - 3 slip or tails로 split 할 수 있음

마. 단점

① 수술전에 plantaris 유무를 알기 어려움

② 2 operative site

③ may be anomalous

④ splitting of lateral stretching interferes with integrity of intact tendon surface → encouraging collagenous adhesion

⑶ Extensor Digitorum Longus(EDL)

가. Anatomy

① origin : proximal part of the anterior compartment

② deep peroneal n. innervation(ant tibial)

③ 2, 3, 4th toe의 EDL의 loss → no disability

: MPJ dorsal aspect에 도달하면서 2, 3, 4th toe로 가는 EDL tendon은 lateral side에서 EDB의 tendon과 join

□ 만일 5th toe의 EDL이 필요할 경우

: 절제하고 distal stump를 4th toe의 EDB에 anastomoses해야함

나. Technique of removal

① serial transverse incision

② superficial peroneal(musculocutaneous) nerve의 손상을 주의

다. 장점

① always present

② 술전에 쉽게 demonstrate

③ common tendon으로 부터 3개 까지의 tendon slip을 얻을 수 있다.

④ slender : for full revascularization

⑤ sufficiently strong: for all purpose

라. 단점

① 흔히 존재하는 accessory slip의 division으로 epitenon이 devoid

→ adhesion ↑

② if 2-3 slips are used → too thick : revascularization곤란

③ 2 operation field

⑷ Flexor Digitorum Superficialis(FDS)

가. Anatomy

① median n. innervation	② 1o flexor of PIP joint

나. Technique of removal : 2 incision

① proximal to base of digit	② distal forearm

다. 장점

① always available	② with same op. field

③ sturdy	④ reasonably accessible

라. 단점

① recurvatum deformity

② reduce efficiency of digital flexion

③ diminished power grasp

④ central avascular necrosis(thick)

마. major utility in tendon transfer : when tendon is present in a lacerated condition, used as a short graft to replace profundus

Tendon Sheath Reconstruction

⑴ 목적

① Bowstring의 방지: multiple pulley 재건이 필요

② synovial environment의 restore: avascular graft의 adequate nutrition

⑵ Donor site

① autogenous grafts of extensor retinaculum

② tendon sheath from the foot

③ autologous veins to reconstruct tendon sheath

Two-Stage Tendon Grafting

: necessary when there is an unsuitable bed for tendon grafting

⑴ 1st stage

① joint contracture release

② skin cover, never repair

③ debridement of tendon ends and scar tissue

④ retinacular pulleys reconstruction utilizing remnants of tendons of extensor retinaculum, autologous tissue transplantation of extensor or flexor retinaculum or vein patch

⑤ flat silicone implant with a Dacron tip : distal fixation suture to profundus stump

⑵ 2nd stage ( 1st stage후 최소한 3개월 뒤 가능)

: after scars are soft & supple → tendon graft를 silicone rod에 suture

Vascularized Tendon Transfer

□ potential donor tendon : EHB based on dorsalis pedis pedicle

cf) FDP를 graft로 제건 후 paradoxical move의 원인

long grafts

lumbricals의 adhesion and contracture

□ Tendon graft시 tendon의 size가 다를 경우 사용하는 방법

① drill hole	② Bunnel suture

③ drill out wire suture

□ Vascularized tendon transfer시 potential donor tendon

① EHB based on dorsalis pedis

② radial forearm flap with palmaris longus

③ groin flap with ext. oblique fascia

EXPERIMENTAL TRANSPLANTATION

Allografts

□ Experimental transplantation

① allograft : tendon → low level of antigenicity

(due to relatively hypocellular & collagen is species specific),

② antigenicity of tissue lies principally in its cells and ground substance

□ Antigenicity를 reduce시키는 methods

① trypsin	② cialit

③ freezing	④ prolonged storage

⑤ irradiation	⑥ lyophilization

Xenograft

: xenograft must satisfy several criteria

① not be antigenic

② not be carcinogenic

③ easily stored and implanted

④ incorporated by host

⑤ its function must simulate that of original part